I would like to change the region, so the balance must first be set to zero.

Sorry, but this is a user to user community, and we can not access your personal data and settings.

You will have to contact the official Apple Support in your country about that. You can start this process by clicking on this online link:

Contact Apple Support

Also make sure to have followed the rest of the steps mentioned in this related article:

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• Cancel subscriptions that block a country or region change: Cancel any subscriptions that block a country or region change, then wait until the end of the subscription period. 
• Wait for pending activity to clear: Wait for any memberships, pre-orders, movie rentals, or Season Passes to complete. You can cancel a pre-order. Also wait for any pending refunds from Apple to process.
• Check your Family Sharing status: If you’re a part of a Family Sharing group, you might not be able to change your country or region. Learn how to leave a Family Sharing group.
• Have a valid payment method ready: You might need to enter a valid payment method for your new country or region. If you don’t want to enter a payment method, wait until you're physically in your new country or region. Then create a new Apple Account.
• Redownload your content: Some types of content might not be available in your new country or region. Redownload your apps, music, movies, TV shows, and books on any devices that you might use to play or read them in the future.

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copied from: Change your Apple Account country or region - Apple Support

Hello ~If you are trying to zero your balance before changing regions…you may purchase an item from the App Store for more than your balance and the remainder will be billed to your credit card on file thus zeroing your balance . You may also go to lower left hand corner and click on Support and they can zero it for you or…

Contact Apple for support and service

Also if you are changing regions take a look through this article as well…

Change your Apple ID country or region - Apple Support

~Katana-San~

Thank you for reaching out. 🤗

There are many parameters that need to be taken before changing regions because currency valuation is not the same across various regions.

If you are changing regions:

• Spend any remaining Apple Account balance: You can spend your remaining balance on the App Store, other Apple services or in some countries and regions, Apple products and accessories. If you’re not sure if you have a balance, check your Apple Account balance.
• Clear a low Apple Account balance: If your balance is less than the cost of a single item in the App Store or other Apple services, learn how to clear your balance.
• Cancel subscriptions that block a country or region change: Cancel any subscriptions that block a country or region change, then wait until the end of the subscription period. 
• Wait for pending activity to clear: Wait for any memberships, pre-orders, movie rentals or Season Passes to complete. You can cancel a pre-order. Also wait for any pending refunds from Apple to process.
• Check your Family Sharing status: If you’re a part of a Family Sharing group, you might not be able to change your country or region. Learn how to leave a Family Sharing group.
• Have a valid payment method ready: You might need to enter a valid payment method for your new country or region. If you don’t want to enter a payment method, wait until you're physically in your new country or region. Then create a new Apple Account.
• Redownload your content: Some types of content might not be available in your new country or region. Redownload your apps, music, movies, TV shows and books on any devices that you might use to play or read them in the future.
• If you need to empty your balance: Contact Apple Support to request a reset of your account balance to zero.

For full details, learn how to → Change Regions for step-by-step instructions.

Good luck! 👋🏼😉

Smiliñ 😎 Brian | Community Volunteer